1. Field of the Invention
This invention relates to a magnetic transfer system for magnetically transferring information carried by a master information carrier to a magnetic recording medium.
2. Description of the Related Art
With an increase in information quantity, there is a demand for a magnetic recording medium which is high in memory capacity, low in cost and preferably requires a short time to read out a necessary part of data (a magnetic recording medium which allows so-called high-speed access). As an example of such a magnetic recording medium, there has been known a high recording density magnetic medium such as a hard disc, a zip (Iomega) and the like. In such a high recording density magnetic medium, the recording area is formed by narrow data tracks. In order to cause a magnetic head to accurately trace such narrow data tracks and reproduce the data at a high S/N ratio, the so-called servo tracking technique has been employed.
In order to perform the servo tracking, it is necessary to write servo information such as servo tracking signals for positioning the data tracks, address signals for the data tracks and reproduction clock signals on the magnetic recording medium as a preformat upon production thereof. At present, such preformat recording is performed by the use of a specialized servo recording apparatus (a servo track writer) However, the preformat recording by the conventional servo recording apparatus is disadvantageous in that it takes a long time since the servo information must be recorded on the magnetic recording medium one by one by the use of a magnetic head, which deteriorates the productivity.
As a method of recording the preformat accurately and efficiently, there has been proposed, for instance, in Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544 and 10(1998)-269566, a magnetic transfer method in which a pattern which is formed on a master information carrier and represents servo information is copied to a magnetic recording medium (a slave medium) by magnetic transfer.
In the magnetic transfer, the magnetization pattern representing the information carried by a master information carrier is magnetically transferred from the master information carrier to a magnetic recording medium (a slave medium) by applying a transfer magnetic field to the slave medium and the master information carrier in close contact with each other, and accordingly, the information carried by the master information carrier can be statically recorded on the slave medium with the relative position between the master information carrier and the slave medium kept constant. Thus, according to the magnetic transfer, the preformat recording can be performed accurately and the time required for the preformat recording is very short.
We, this applicant, have proposed in Japanese Unexamined Patent Publication No. 2001-14667 a method of magnetic transfer in which the magnetization pattern on a master information carrier is magnetically transferred to the magnetic layer of a slave medium by forming the magnetic layer on the surface of the protruding portions of the master information carrier of soft magnetic material which is small in coercive force, initially magnetizing the magnetic layer of the slave medium in one direction of the recording tracks and applying a transfer magnetic field to the slave medium in the direction opposite to the direction of the initial-magnetization with the magnetic layer of the slave medium held in close contact with the soft magnetic layer of the master information carrier.
The magnetic transfer system for carrying out the magnetic transfer described above basically comprises a means for holding a magnetic recording medium (a slave medium), a means for conveying the magnetic recording medium and a magnetic transfer apparatus which applies a magnetic field to the slave medium and a master information carrier holding the slave medium and the master information carrier in close contact with each other, and materials such as rubber containing therein chlorine or sulfur are used in parts such as the means for holding the magnetic recording medium, the means for conveying the magnetic recording medium and the magnetic transfer apparatus which are brought into contact with the slave medium. However, there has been a problem that the magnetic recording medium (the slave medium), especially a hard disc, is readily attacked by chlorine, sulfur or nitric oxide and is eroded when brought into contact therewith. Further, it has been found that when residue containing therein chlorine, sulfur or nitric oxide adheres to the master information carrier, the magnetic layer on the master information carrier is eroded as well as the slave medium and the service life of the master information carrier is greatly shortened.